1. Field of the Invention
The present invention relates generally to fluid flow control systems and, more particularly, to flow controllers employing peristaltic pumps. The invention is particularly advantageous for use in conveying biological or biochemical fluids such as blood or other fluids known to clog or corrode elements of prior flow controllers.
2. Description of the Prior Art
U.S. Pat. No. 3,997,420, assigned to the assignee of the present invention, describes a flow cell for use in blood chemistry analyses and in particular for determining the pH, PCO.sub.2 and PO.sub.2 of blood. The cell employs pH, PCO.sub.2, and PO.sub.2 measuring electrodes mounted adjacent a sample passage extending through the cell. A blood sample is collected in a conventional syringe and the syringe plunger is actuated to drive the sample through the flow cell passage in contact with each of the measuring electrodes. A wash solution is then conveyed through the passage to discharge the remaining sample therefrom to prepare the flow cell for receipt of the next injected sample. In addition, a calibration solution is periodically conveyed through the passage, as required, to calibrate the measuring electrodes.
Though the foregoing apparatus represents an advance in the art of automated blood chemistry analysis, it employs a complicated array of pumps and valves for conveying the various fluids through the analyzer. When conveying blood or other biological or biochemical fluids, the valves and other elements of the control system can become contaminated or fouled by foreign material in the blood or by blood clots and are further subjected to corrosion over time by the salts and other blood components. Moreover, it is possible for dead volumes to occur in the flow system inhibiting the inefficient flow of fluid through the analyzer.